until after the INIT stage. I don't think this particularly matters for
parameters, since if the URL is unknown it almost certainly means that we
will not need to do the custom parameter loading anyway, but let's just
make sure.
This also knocks a "known issue" off my list, and opens up the possibility
of remixed items loading content packs from a relative URL.
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4646 542714f4-19e9-0310-aa3c-eee0fc999fb1